#region Copyright & License

//
// Copyright 2001-2005 The Apache Software Foundation
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//

#endregion

using System;
using System.Collections;
using log4net.Util;

namespace log4net.Core {
  /// <summary>
  /// A strongly-typed collection of <see cref="Level"/> objects.
  /// </summary>
  /// <author>Nicko Cadell</author>
  public class LevelCollection : ICollection, IList, IEnumerable, ICloneable {
    #region Interfaces

    /// <summary>
    /// Supports type-safe iteration over a <see cref="LevelCollection"/>.
    /// </summary>
    public interface ILevelCollectionEnumerator {
      /// <summary>
      /// Gets the current element in the collection.
      /// </summary>
      Level Current { get; }

      /// <summary>
      /// Advances the enumerator to the next element in the collection.
      /// </summary>
      /// <returns>
      /// <c>true</c> if the enumerator was successfully advanced to the next element; 
      /// <c>false</c> if the enumerator has passed the end of the collection.
      /// </returns>
      /// <exception cref="InvalidOperationException">
      /// The collection was modified after the enumerator was created.
      /// </exception>
      bool MoveNext();

      /// <summary>
      /// Sets the enumerator to its initial position, before the first element in the collection.
      /// </summary>
      void Reset();
    }

    #endregion

    const int DEFAULT_CAPACITY = 16;

    #region Implementation (data)

    Level[] m_array;
    int m_count;
    int m_version;

    #endregion

    #region Static Wrappers

    /// <summary>
    /// Creates a read-only wrapper for a <c>LevelCollection</c> instance.
    /// </summary>
    /// <param name="list">list to create a readonly wrapper arround</param>
    /// <returns>
    /// A <c>LevelCollection</c> wrapper that is read-only.
    /// </returns>
    public static LevelCollection ReadOnly(LevelCollection list) {
      if (list == null)
        throw new ArgumentNullException("list");

      return new ReadOnlyLevelCollection(list);
    }

    #endregion

    #region Constructors

    /// <summary>
    /// Initializes a new instance of the <c>LevelCollection</c> class
    /// that is empty and has the default initial capacity.
    /// </summary>
    public LevelCollection() {
      m_array = new Level[DEFAULT_CAPACITY];
    }

    /// <summary>
    /// Initializes a new instance of the <c>LevelCollection</c> class
    /// that has the specified initial capacity.
    /// </summary>
    /// <param name="capacity">
    /// The number of elements that the new <c>LevelCollection</c> is initially capable of storing.
    /// </param>
    public LevelCollection(int capacity) {
      m_array = new Level[capacity];
    }

    /// <summary>
    /// Initializes a new instance of the <c>LevelCollection</c> class
    /// that contains elements copied from the specified <c>LevelCollection</c>.
    /// </summary>
    /// <param name="c">The <c>LevelCollection</c> whose elements are copied to the new collection.</param>
    public LevelCollection(LevelCollection c) {
      m_array = new Level[c.Count];
      AddRange(c);
    }

    /// <summary>
    /// Initializes a new instance of the <c>LevelCollection</c> class
    /// that contains elements copied from the specified <see cref="Level"/> array.
    /// </summary>
    /// <param name="a">The <see cref="Level"/> array whose elements are copied to the new list.</param>
    public LevelCollection(Level[] a) {
      m_array = new Level[a.Length];
      AddRange(a);
    }

    /// <summary>
    /// Initializes a new instance of the <c>LevelCollection</c> class
    /// that contains elements copied from the specified <see cref="Level"/> collection.
    /// </summary>
    /// <param name="col">The <see cref="Level"/> collection whose elements are copied to the new list.</param>
    public LevelCollection(ICollection col) {
      m_array = new Level[col.Count];
      AddRange(col);
    }

    /// <summary>
    /// Allow subclasses to avoid our default constructors
    /// </summary>
    /// <param name="tag"></param>
    protected internal LevelCollection(Tag tag) {
      m_array = null;
    }

    /// <summary>
    /// Type visible only to our subclasses
    /// Used to access protected constructor
    /// </summary>
    protected internal enum Tag {
      /// <summary>
      /// A value
      /// </summary>
      Default
    }

    #endregion

    #region Operations (type-safe ICollection)

    /// <summary>
    /// Gets the number of elements actually contained in the <c>LevelCollection</c>.
    /// </summary>
    public virtual int Count {
      get { return m_count; }
    }

    /// <summary>
    /// Gets a value indicating whether access to the collection is synchronized (thread-safe).
    /// </summary>
    /// <value>true if access to the ICollection is synchronized (thread-safe); otherwise, false.</value>
    public virtual bool IsSynchronized {
      get { return m_array.IsSynchronized; }
    }

    /// <summary>
    /// Gets an object that can be used to synchronize access to the collection.
    /// </summary>
    public virtual object SyncRoot {
      get { return m_array.SyncRoot; }
    }

    /// <summary>
    /// Copies the entire <c>LevelCollection</c> to a one-dimensional
    /// <see cref="Level"/> array.
    /// </summary>
    /// <param name="array">The one-dimensional <see cref="Level"/> array to copy to.</param>
    public virtual void CopyTo(Level[] array) {
      CopyTo(array, 0);
    }

    /// <summary>
    /// Copies the entire <c>LevelCollection</c> to a one-dimensional
    /// <see cref="Level"/> array, starting at the specified index of the target array.
    /// </summary>
    /// <param name="array">The one-dimensional <see cref="Level"/> array to copy to.</param>
    /// <param name="start">The zero-based index in <paramref name="array"/> at which copying begins.</param>
    public virtual void CopyTo(Level[] array, int start) {
      if (m_count > array.GetUpperBound(0) + 1 - start)
        throw new ArgumentException("Destination array was not long enough.");

      Array.Copy(m_array, 0, array, start, m_count);
    }

    #endregion

    #region Operations (type-safe IList)

    /// <summary>
    /// Gets or sets the <see cref="Level"/> at the specified index.
    /// </summary>
    /// <param name="index">The zero-based index of the element to get or set.</param>
    /// <exception cref="ArgumentOutOfRangeException">
    /// <para><paramref name="index"/> is less than zero</para>
    /// <para>-or-</para>
    /// <para><paramref name="index"/> is equal to or greater than <see cref="LevelCollection.Count"/>.</para>
    /// </exception>
    public virtual Level this[int index] {
      get {
        ValidateIndex(index); // throws
        return m_array[index];
      }
      set {
        ValidateIndex(index); // throws
        ++m_version;
        m_array[index] = value;
      }
    }

    #region ICloneable Members

    /// <summary>
    /// Creates a shallow copy of the <see cref="LevelCollection"/>.
    /// </summary>
    /// <returns>A new <see cref="LevelCollection"/> with a shallow copy of the collection data.</returns>
    public virtual object Clone() {
      var newCol = new LevelCollection(m_count);
      Array.Copy(m_array, 0, newCol.m_array, 0, m_count);
      newCol.m_count = m_count;
      newCol.m_version = m_version;

      return newCol;
    }

    #endregion

    #region IList Members

    /// <summary>
    /// Removes all elements from the <c>LevelCollection</c>.
    /// </summary>
    public virtual void Clear() {
      ++m_version;
      m_array = new Level[DEFAULT_CAPACITY];
      m_count = 0;
    }

    /// <summary>
    /// Gets a value indicating whether the collection has a fixed size.
    /// </summary>
    /// <value>true if the collection has a fixed size; otherwise, false. The default is false</value>
    public virtual bool IsFixedSize {
      get { return false; }
    }

    /// <summary>
    /// Gets a value indicating whether the IList is read-only.
    /// </summary>
    /// <value>true if the collection is read-only; otherwise, false. The default is false</value>
    public virtual bool IsReadOnly {
      get { return false; }
    }

    #endregion

    /// <summary>
    /// Adds a <see cref="Level"/> to the end of the <c>LevelCollection</c>.
    /// </summary>
    /// <param name="item">The <see cref="Level"/> to be added to the end of the <c>LevelCollection</c>.</param>
    /// <returns>The index at which the value has been added.</returns>
    public virtual int Add(Level item) {
      if (m_count == m_array.Length)
        EnsureCapacity(m_count + 1);

      m_array[m_count] = item;
      m_version++;

      return m_count++;
    }

    /// <summary>
    /// Determines whether a given <see cref="Level"/> is in the <c>LevelCollection</c>.
    /// </summary>
    /// <param name="item">The <see cref="Level"/> to check for.</param>
    /// <returns><c>true</c> if <paramref name="item"/> is found in the <c>LevelCollection</c>; otherwise, <c>false</c>.</returns>
    public virtual bool Contains(Level item) {
      for (int i = 0; i != m_count; ++i)
        if (m_array[i].Equals(item))
          return true;
      return false;
    }

    /// <summary>
    /// Returns the zero-based index of the first occurrence of a <see cref="Level"/>
    /// in the <c>LevelCollection</c>.
    /// </summary>
    /// <param name="item">The <see cref="Level"/> to locate in the <c>LevelCollection</c>.</param>
    /// <returns>
    /// The zero-based index of the first occurrence of <paramref name="item"/> 
    /// in the entire <c>LevelCollection</c>, if found; otherwise, -1.
    ///	</returns>
    public virtual int IndexOf(Level item) {
      for (int i = 0; i != m_count; ++i)
        if (m_array[i].Equals(item))
          return i;
      return -1;
    }

    /// <summary>
    /// Inserts an element into the <c>LevelCollection</c> at the specified index.
    /// </summary>
    /// <param name="index">The zero-based index at which <paramref name="item"/> should be inserted.</param>
    /// <param name="item">The <see cref="Level"/> to insert.</param>
    /// <exception cref="ArgumentOutOfRangeException">
    /// <para><paramref name="index"/> is less than zero</para>
    /// <para>-or-</para>
    /// <para><paramref name="index"/> is equal to or greater than <see cref="LevelCollection.Count"/>.</para>
    /// </exception>
    public virtual void Insert(int index, Level item) {
      ValidateIndex(index, true); // throws

      if (m_count == m_array.Length)
        EnsureCapacity(m_count + 1);

      if (index < m_count)
        Array.Copy(m_array, index, m_array, index + 1, m_count - index);

      m_array[index] = item;
      m_count++;
      m_version++;
    }

    /// <summary>
    /// Removes the first occurrence of a specific <see cref="Level"/> from the <c>LevelCollection</c>.
    /// </summary>
    /// <param name="item">The <see cref="Level"/> to remove from the <c>LevelCollection</c>.</param>
    /// <exception cref="ArgumentException">
    /// The specified <see cref="Level"/> was not found in the <c>LevelCollection</c>.
    /// </exception>
    public virtual void Remove(Level item) {
      int i = IndexOf(item);
      if (i < 0)
        throw new ArgumentException(
          "Cannot remove the specified item because it was not found in the specified Collection.");

      ++m_version;
      RemoveAt(i);
    }

    /// <summary>
    /// Removes the element at the specified index of the <c>LevelCollection</c>.
    /// </summary>
    /// <param name="index">The zero-based index of the element to remove.</param>
    /// <exception cref="ArgumentOutOfRangeException">
    /// <para><paramref name="index"/> is less than zero</para>
    /// <para>-or-</para>
    /// <para><paramref name="index"/> is equal to or greater than <see cref="LevelCollection.Count"/>.</para>
    /// </exception>
    public virtual void RemoveAt(int index) {
      ValidateIndex(index); // throws

      m_count--;

      if (index < m_count)
        Array.Copy(m_array, index + 1, m_array, index, m_count - index);

      // We can't set the deleted entry equal to null, because it might be a value type.
      // Instead, we'll create an empty single-element array of the right type and copy it 
      // over the entry we want to erase.
      var temp = new Level[1];
      Array.Copy(temp, 0, m_array, m_count, 1);
      m_version++;
    }

    #endregion

    #region Operations (type-safe IEnumerable)

    /// <summary>
    /// Returns an enumerator that can iterate through the <c>LevelCollection</c>.
    /// </summary>
    /// <returns>An <see cref="Enumerator"/> for the entire <c>LevelCollection</c>.</returns>
    public virtual ILevelCollectionEnumerator GetEnumerator() {
      return new Enumerator(this);
    }

    #endregion

    #region Public helpers (just to mimic some nice features of ArrayList)

    /// <summary>
    /// Gets or sets the number of elements the <c>LevelCollection</c> can contain.
    /// </summary>
    public virtual int Capacity {
      get { return m_array.Length; }
      set {
        if (value < m_count)
          value = m_count;

        if (value != m_array.Length)
          if (value > 0) {
            var temp = new Level[value];
            Array.Copy(m_array, 0, temp, 0, m_count);
            m_array = temp;
          } else
            m_array = new Level[DEFAULT_CAPACITY];
      }
    }

    /// <summary>
    /// Adds the elements of another <c>LevelCollection</c> to the current <c>LevelCollection</c>.
    /// </summary>
    /// <param name="x">The <c>LevelCollection</c> whose elements should be added to the end of the current <c>LevelCollection</c>.</param>
    /// <returns>The new <see cref="LevelCollection.Count"/> of the <c>LevelCollection</c>.</returns>
    public virtual int AddRange(LevelCollection x) {
      if (m_count + x.Count >= m_array.Length)
        EnsureCapacity(m_count + x.Count);

      Array.Copy(x.m_array, 0, m_array, m_count, x.Count);
      m_count += x.Count;
      m_version++;

      return m_count;
    }

    /// <summary>
    /// Adds the elements of a <see cref="Level"/> array to the current <c>LevelCollection</c>.
    /// </summary>
    /// <param name="x">The <see cref="Level"/> array whose elements should be added to the end of the <c>LevelCollection</c>.</param>
    /// <returns>The new <see cref="LevelCollection.Count"/> of the <c>LevelCollection</c>.</returns>
    public virtual int AddRange(Level[] x) {
      if (m_count + x.Length >= m_array.Length)
        EnsureCapacity(m_count + x.Length);

      Array.Copy(x, 0, m_array, m_count, x.Length);
      m_count += x.Length;
      m_version++;

      return m_count;
    }

    /// <summary>
    /// Adds the elements of a <see cref="Level"/> collection to the current <c>LevelCollection</c>.
    /// </summary>
    /// <param name="col">The <see cref="Level"/> collection whose elements should be added to the end of the <c>LevelCollection</c>.</param>
    /// <returns>The new <see cref="LevelCollection.Count"/> of the <c>LevelCollection</c>.</returns>
    public virtual int AddRange(ICollection col) {
      if (m_count + col.Count >= m_array.Length)
        EnsureCapacity(m_count + col.Count);

      foreach (object item in col)
        Add((Level) item);

      return m_count;
    }

    /// <summary>
    /// Sets the capacity to the actual number of elements.
    /// </summary>
    public virtual void TrimToSize() {
      Capacity = m_count;
    }

    #endregion

    #region Implementation (helpers)

    /// <exception cref="ArgumentOutOfRangeException">
    /// <para><paramref name="index"/> is less than zero</para>
    /// <para>-or-</para>
    /// <para><paramref name="index"/> is equal to or greater than <see cref="LevelCollection.Count"/>.</para>
    /// </exception>
    void ValidateIndex(int i) {
      ValidateIndex(i, false);
    }

    /// <exception cref="ArgumentOutOfRangeException">
    /// <para><paramref name="index"/> is less than zero</para>
    /// <para>-or-</para>
    /// <para><paramref name="index"/> is equal to or greater than <see cref="LevelCollection.Count"/>.</para>
    /// </exception>
    void ValidateIndex(int i, bool allowEqualEnd) {
      int max = (allowEqualEnd) ? (m_count) : (m_count - 1);
      if (i < 0 || i > max)
        throw SystemInfo.CreateArgumentOutOfRangeException("i", i,
                                                           "Index was out of range. Must be non-negative and less than the size of the collection. [" +
                                                           i +
                                                           "] Specified argument was out of the range of valid values.");
    }

    void EnsureCapacity(int min) {
      int newCapacity = ((m_array.Length == 0) ? DEFAULT_CAPACITY : m_array.Length*2);
      if (newCapacity < min)
        newCapacity = min;

      Capacity = newCapacity;
    }

    #endregion

    #region Implementation (ICollection)

    void ICollection.CopyTo(Array array, int start) {
      Array.Copy(m_array, 0, array, start, m_count);
    }

    #endregion

    #region Implementation (IList)

    object IList.this[int i] {
      get { return this[i]; }
      set { this[i] = (Level) value; }
    }

    int IList.Add(object x) {
      return Add((Level) x);
    }

    bool IList.Contains(object x) {
      return Contains((Level) x);
    }

    int IList.IndexOf(object x) {
      return IndexOf((Level) x);
    }

    void IList.Insert(int pos, object x) {
      Insert(pos, (Level) x);
    }

    void IList.Remove(object x) {
      Remove((Level) x);
    }

    void IList.RemoveAt(int pos) {
      RemoveAt(pos);
    }

    #endregion

    #region Implementation (IEnumerable)

    IEnumerator IEnumerable.GetEnumerator() {
      return (IEnumerator) (GetEnumerator());
    }

    #endregion

    #region Nested type: Enumerator

    /// <summary>
    /// Supports simple iteration over a <see cref="LevelCollection"/>.
    /// </summary>
    sealed class Enumerator : IEnumerator, ILevelCollectionEnumerator {
      #region Implementation (data)

      readonly LevelCollection m_collection;
      readonly int m_version;
      int m_index;

      #endregion

      #region Construction

      /// <summary>
      /// Initializes a new instance of the <c>Enumerator</c> class.
      /// </summary>
      /// <param name="tc"></param>
      internal Enumerator(LevelCollection tc) {
        m_collection = tc;
        m_index = -1;
        m_version = tc.m_version;
      }

      #endregion

      #region Operations (type-safe IEnumerator)

      #region IEnumerator Members

      /// <summary>
      /// Advances the enumerator to the next element in the collection.
      /// </summary>
      /// <returns>
      /// <c>true</c> if the enumerator was successfully advanced to the next element; 
      /// <c>false</c> if the enumerator has passed the end of the collection.
      /// </returns>
      /// <exception cref="InvalidOperationException">
      /// The collection was modified after the enumerator was created.
      /// </exception>
      public bool MoveNext() {
        if (m_version != m_collection.m_version)
          throw new InvalidOperationException(
            "Collection was modified; enumeration operation may not execute.");

        ++m_index;
        return (m_index < m_collection.Count);
      }

      /// <summary>
      /// Sets the enumerator to its initial position, before the first element in the collection.
      /// </summary>
      public void Reset() {
        m_index = -1;
      }

      #endregion

      #region ILevelCollectionEnumerator Members

      /// <summary>
      /// Gets the current element in the collection.
      /// </summary>
      public Level Current {
        get { return m_collection[m_index]; }
      }

      #endregion

      #endregion

      #region Implementation (IEnumerator)

      object IEnumerator.Current {
        get { return Current; }
      }

      #endregion
    }

    #endregion

    #region Nested Read Only Wrapper class

    sealed class ReadOnlyLevelCollection : LevelCollection {
      #region Implementation (data)

      readonly LevelCollection m_collection;

      #endregion

      #region Construction

      internal ReadOnlyLevelCollection(LevelCollection list) : base(Tag.Default) {
        m_collection = list;
      }

      #endregion

      #region Type-safe ICollection

      public override int Count {
        get { return m_collection.Count; }
      }

      public override bool IsSynchronized {
        get { return m_collection.IsSynchronized; }
      }

      public override object SyncRoot {
        get { return m_collection.SyncRoot; }
      }

      public override void CopyTo(Level[] array) {
        m_collection.CopyTo(array);
      }

      public override void CopyTo(Level[] array, int start) {
        m_collection.CopyTo(array, start);
      }

      #endregion

      #region Type-safe IList

      public override Level this[int i] {
        get { return m_collection[i]; }
        set { throw new NotSupportedException("This is a Read Only Collection and can not be modified"); }
      }

      public override bool IsFixedSize {
        get { return true; }
      }

      public override bool IsReadOnly {
        get { return true; }
      }

      public override int Add(Level x) {
        throw new NotSupportedException("This is a Read Only Collection and can not be modified");
      }

      public override void Clear() {
        throw new NotSupportedException("This is a Read Only Collection and can not be modified");
      }

      public override bool Contains(Level x) {
        return m_collection.Contains(x);
      }

      public override int IndexOf(Level x) {
        return m_collection.IndexOf(x);
      }

      public override void Insert(int pos, Level x) {
        throw new NotSupportedException("This is a Read Only Collection and can not be modified");
      }

      public override void Remove(Level x) {
        throw new NotSupportedException("This is a Read Only Collection and can not be modified");
      }

      public override void RemoveAt(int pos) {
        throw new NotSupportedException("This is a Read Only Collection and can not be modified");
      }

      #endregion

      #region Type-safe IEnumerable

      public override ILevelCollectionEnumerator GetEnumerator() {
        return m_collection.GetEnumerator();
      }

      #endregion

      #region Public Helpers

      // (just to mimic some nice features of ArrayList)
      public override int Capacity {
        get { return m_collection.Capacity; }
        set { throw new NotSupportedException("This is a Read Only Collection and can not be modified"); }
      }

      public override int AddRange(LevelCollection x) {
        throw new NotSupportedException("This is a Read Only Collection and can not be modified");
      }

      public override int AddRange(Level[] x) {
        throw new NotSupportedException("This is a Read Only Collection and can not be modified");
      }

      #endregion
    }

    #endregion
  }
}